U.S. patent application number 15/307666 was filed with the patent office on 2017-02-23 for film for sheet fed printing, sheets formed from such film and labels formed from such sheets.
The applicant listed for this patent is Taghleef Industries Inc.. Invention is credited to Bruce S. MARKS.
Application Number | 20170050458 15/307666 |
Document ID | / |
Family ID | 53190025 |
Filed Date | 2017-02-23 |
United States Patent
Application |
20170050458 |
Kind Code |
A1 |
MARKS; Bruce S. |
February 23, 2017 |
FILM FOR SHEET FED PRINTING, SHEETS FORMED FROM SUCH FILM AND
LABELS FORMED FROM SUCH SHEETS
Abstract
A plurality of plastic sheets to be fed into a high speed
printer for forming printed labels and similar articles and a stack
of printed labels formed form the sheets. Each of the sheets or
labels includes a core layer and opposed, upper and lower outer
skin layers. The upper outer skin layer includes a polyolefin
polymer as the predominant component, by weight, thereof and is
capable of receiving printed indicia thereon. The core layer
includes a polyolefin polymer as the predominant component, by
weight, of the core layer; preferably a high crystallinity
polypropylene homopolymer. The lower outer skin layer includes a
polyolefin polymer as the predominant component by weight therein;
the improvement wherein the lower outer skin layer includes a blend
of organic and inorganic antiblocking agents or a blend of
inorganic antiblocking agents; the blend including less than 10%,
by weight, of the lower outer skin layer.
Inventors: |
MARKS; Bruce S.; (Glen
Mills, PA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Taghleef Industries Inc. |
Newark |
DE |
US |
|
|
Family ID: |
53190025 |
Appl. No.: |
15/307666 |
Filed: |
April 29, 2015 |
PCT Filed: |
April 29, 2015 |
PCT NO: |
PCT/US2015/028281 |
371 Date: |
October 28, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61986484 |
Apr 30, 2014 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B32B 27/08 20130101;
B41M 5/502 20130101; B41M 5/5254 20130101; B32B 2264/102 20130101;
G09F 2003/0201 20130101; B32B 27/18 20130101; B41M 2205/34
20130101; B32B 2264/12 20130101; B32B 2307/75 20130101; B41M 5/5218
20130101; B32B 27/32 20130101; B32B 2264/10 20130101; B41M 5/52
20130101; G09F 2003/0257 20130101; B32B 2307/518 20130101; B32B
2519/00 20130101; G09F 3/02 20130101; B32B 2307/746 20130101; B32B
2250/242 20130101; B41M 5/508 20130101; B41M 2205/36 20130101; B32B
2255/10 20130101; G09F 2003/0226 20130101; B41M 5/504 20130101;
B32B 27/20 20130101 |
International
Class: |
B41M 5/52 20060101
B41M005/52; G09F 3/02 20060101 G09F003/02; B32B 27/32 20060101
B32B027/32; B41M 5/50 20060101 B41M005/50; B32B 27/08 20060101
B32B027/08; B32B 27/20 20060101 B32B027/20 |
Claims
1. A plurality of plastic sheets cut from a continuous roll of
plastic film to be fed into a high speed printer for forming
printed labels and similar articles, each of said sheets including
a core layer and opposed, upper and lower outer skin layers, said
upper outer skin layer including a polyolefin polymer as the
predominate component, by weight, thereof and being capable of
receiving printed indicia thereon that is applied by said high
speed printer, said core layer including a polyolefin polymer as
the predominant component, by weight, of the core layer, said lower
outer skin layer including a polyolefin polymer as the predominant
component, by weight, of said lower outer skin layer, the
improvement wherein said lower outer skin layer includes a blend of
organic and inorganic antiblocking agents, said blend including
less than 10%, by weight, of the lower outer skin layer.
2. The plurality of plastic sheets as specified in claim 1, wherein
said blend includes two inorganic antiblocking agents, one of said
inorganic antiblocking agents being roughly spherical with an
irregular surface and a second of said inorganic antiblocking
agents being substantially plate-like.
3. The plurality of plastic sheets as specified in claim 1, further
including a coupling agent for aiding in adhering said blend of
organic and inorganic antiblocking agents in said lower outer skin
layer.
4. The plurality of plastic sheets as specified in claim 1, wherein
said blend includes two inorganic antiblocking agents, one of said
inorganic antiblocking agents being roughly spherical with an
irregular surface and a second of said inorganic antiblocking
agents being substantially plate-like, said second inorganic
antiblocking agent being talc.
5. The plurality of plastic sheets as specified in claim 1, wherein
said organic antiblocking agent includes polymethylmethacrylate
(PMMA) and said blend further includes two inorganic antiblocking
agents, one of said inorganic antiblocking agent being roughly
spherical with an irregular surface and a second of said inorganic
antiblocking agents being substantially plate-like, said second
inorganic antiblocking agent being talc, and a coupling agent for
aiding in adhering said blend in said lower outer skin layer.
6. The plurality of plastic sheets as specified in claim 1, wherein
said blend includes two inorganic antiblocking agents, one of said
inorganic antiblocking agents being roughly spherical with an
irregular surface and a second of said inorganic antiblocking
agents being substantially plate-like, said second inorganic
antiblocking agent being less than 2% by weight of said lower outer
skin layer, said lower outer skin layer including a weight percent
of the organic antiblocking agent less than the weight percent of
the second inorganic antiblocking agent.
7. The plurality of plastic sheets as specified in claim 1, wherein
said blend includes two inorganic antiblocking agents, one of said
inorganic antiblocking agents being roughly spherical with an
irregular surface and a second of said inorganic antiblocking
agents being substantially plate-like, said second inorganic
antiblocking agent being less than 2% by weight of said lower outer
skin layer, said lower outer skin layer including a weight percent
of the organic antiblocking agent less than the weight percent of
the second inorganic antiblocking agent, said lower skin layer
including a coupling agent for aiding in adhering the inorganic and
organic antiblocking agents in said lower skin layer.
8. The plurality of plastic sheets as specified in claim 1, wherein
said blend includes two inorganic antiblocking agents, one of said
inorganic antiblocking agents being roughly spherical with an
irregular surface and a second of said inorganic antiblocking
agents being substantially plate-like, said second inorganic
antiblocking agent being less than 2% by weight of said lower outer
skin layer, said lower outer skin layer including a weight percent
of the organic antiblocking agent less than the weight percent of
the second inorganic antiblocking agent, said lower skin layer
including maleic anhydride-modified polypropylene homopolymer as a
coupling agent for aiding in adhering the inorganic and organic
antiblocking agents in said lower skin layer.
9. The plurality of plastic sheets as specified in claim 1, wherein
said blend includes two inorganic antiblocking agents, one of said
inorganic antiblocking agents being roughly spherical with an
irregular surface and a second of said inorganic antiblocking
agents being substantially plate-like, said second inorganic
antiblocking agent being less than 2% by weight of said lower outer
skin layer and said organic antiblocking agent and said roughly
spherical inorganic antiblocking agent each being less than 1% by
weight of said lower outer skin layer.
10. The plurality of plastic sheets as specified in claim 1,
wherein said blend includes two inorganic antiblocking agents, one
of said inorganic antiblocking agents being roughly spherical with
an irregular surface and a second of said inorganic antiblocking
agents being substantially plate-like, said second inorganic
antiblocking agent being less than 2% by weight of said lower outer
skin layer and said organic antiblocking agent and said
substantially roughly spherical antiblocking agents each being less
than 1% by weight of said lower outer skin layer, said lower skin
layer including a coupling agent for aiding in adhering the
inorganic and organic antiblocking agents in said lower skin
layer.
11. The plurality of plastic sheets as specified in claim 1,
wherein said blend includes two inorganic antiblocking agents, one
of said inorganic antiblocking agents being roughly spherical with
an irregular surface and a second of said inorganic antiblocking
agents being substantially plate-like, said second inorganic
antiblocking agent being less than 2% by weight of said lower outer
skin layer and said organic antiblocking agent and said roughly
spherical inorganic antiblocking agents each being less than 0.5%
by weight of said lower outer skin layer.
12. The plurality of plastic sheets as specified in claim 1,
wherein said blend includes two inorganic antiblocking agents, one
of said inorganic antiblocking agents being roughly spherical with
an irregular surface and a second of said inorganic antiblocking
agents being substantially plate-like, said second inorganic
antiblocking agent being less than 2% by weight of said lower outer
skin layer and said organic antiblocking agent and said roughly
spherical inorganic antiblocking agents each being less than 0.5%
by weight of said lower outer skin layer, the weight percent of
said substantially round inorganic antiblocking agent and said
organic antiblocking agent being substantially the same.
13. Printed labels cut from the sheets of claim 1 and maintained in
a stack to be individually fed from the stack for use in labeling
articles.
14. Printed labels cut from the sheets of claim 1 and maintained in
a stack to be individually fed from the stack for use in labeling
preformed articles.
15. Printed labels cut from the sheets of claim 1 and maintained in
a stack to be individually fed from the stack for use in an in-mold
labeling operation.
16. The plurality of plastic sheets as specified in claim 1, said
plurality of plastic sheets including adjacent leading and trailing
plastic sheets, said leading plastic sheets being directed through
the high speed printer prior to adjacent, trailing sheets, said
lower outer skin layer of the leading plastic sheets being at least
in partial engagement with said upper outer skin layer of the
adjacent trailing plastic sheet.
17. The plurality of plastic sheets as specified in claim 16, said
leading and adjacent trailing sheets being retained in a stack from
which the leading sheets and adjacent trailing sheets are fed into
and through the high speed printer in a shingled arrangement
wherein distal ends of the lower outer skin layers of the leading
sheets engage upper proximal outer skin layers of the trailing
sheets.
18. A plurality of labels in a stack, each label including a core
layer and opposed, upper and lower outer skin layers, said upper
outer skin layer including a polyolefin polymer as the predominate
component, by weight, thereof and being capable of receiving
printed indicia thereon that is applied by said high speed printer,
said core layer including a polyolefin polymer as the predominant
component, by weight, of the core layer, said lower outer skin
layer including a polyolefin polymer as the predominant component,
by weight, of said lower outer skin layer, the improvement wherein
said lower outer skin layer includes a blend of organic and
inorganic antiblocking agents, said blend including less than 10%,
by weight, of the lower outer skin layer, the lower outer skin
layer of each of the labels engaging an outer skin layer of an
adjacent label below said each of the labels.
19. The plurality of labels as specified in claim 18, wherein the
lower outer skin layer of each of said sheets includes less than 5%
talc, by weight, based on the weight of the lower outer skin layer,
as an inorganic antiblocking agent, said organic antiblocking
agents including PMMA being present in a weight percentage of less
than 1 based on the weight of the lower outer skin layer, and a
maleic anhydride-modified polypropylene homopolymer for aiding in
adhering the talc in said lower outer skin layer.
20. The plurality of labels as specified in claim 18, wherein said
lower outer skin layer of each of said sheets includes less than 5%
talc, by weight, based on the weight of the lower outer skin layer,
as an inorganic antiblocking agent, and a maleic anhydride-modified
polypropylene homopolymer for aiding in adhering the talc in said
lower outer skin layer, said organic antiblocking agents including
PMMA being present in a weight percentage of less than 1 based on
the weight of the lower outer skin layer and said maleic
anhydride-modified polypropylene homopolymer is prepared by
utilizing about 0.5% maleic anhydride.
21. The plurality of labels as specified in claim 18, wherein the
lower outer skin layer of each of said sheets includes between
1%-5% talc, by weight, based on the weight of the lower outer skin
layer, as an inorganic antiblocking agent, and a coupling agent for
aiding in adhering the talc in said lower outer skin layer, said
organic antiblocking agents including PMMA being present in a
weight percentage of less than 0.5%, based on the weight of the
lower outer skin layer.
22. The plurality of labels as specified in claim 20, wherein said
coupling agent is a maleic anhydride-modified polypropylene
homopolymer.
23. The plurality of labels as specified in claim 18, wherein the
lower outer skin layer of each of said sheets includes between
1%-5% talc, by weight, based on the weight of the lower outer skin
layer, as an inorganic antiblocking agent and a maleic
anhydride-modified polypropylene homopolymer for aiding in adhering
the talc in said lower outer skin layer, said organic antiblocking
agents including PMMA being present in a weight percentage of less
than 5.0%, based on the weight of the lower outer skin layer and
said maleic anhydride-modified grafted homopolymer polypropylene
being present in a weight percent of about 5% based on the weight
of the lower outer skin layer.
24. A plurality of plastic sheets cut from a continuous roll of
plastic film to be fed into a high speed printer for forming
printed labels and similar articles, each of said sheets including
a core layer and opposed, upper and lower outer skin layers, said
upper outer skin layer including a polyolefin polymer as the
predominate component, by weight, thereof and being capable of
receiving printed indicia thereon that is applied by said high
speed printer, said core layer including a polyolefin polymer as
the predominant component, by weight, of the core layer, said lower
outer skin layer including a polyolefin polymer as the predominant
component, by weight, of said lower outer skin layer, the
improvement wherein said lower outer skin layer includes a blend of
inorganic antiblocking agents, said blend including less than 10%,
by weight, of the lower outer skin layer.
25. The plurality of plastic sheets as specified in claim 24,
wherein said blend includes two inorganic antiblocking agents, one
of said inorganic antiblocking agents being roughly spherical with
an irregular surface and a second of said inorganic antiblocking
agents being substantially plate-like.
26. The plurality of plastic sheets as specified in claim 23,
further including a coupling agent for aiding in adhering said
blend of inorganic antiblocking agents in said lower outer skin
layer.
27. The plurality of plastic sheets as specified in claim 23,
wherein said blend includes two inorganic antiblocking agents, one
of said inorganic antiblocking agents being roughly spherical with
an irregular surface and a second of said inorganic antiblocking
agents being substantially plate-like, said second inorganic
antiblocking agent being talc.
28. The plurality of plastic sheets as specified in claim 27,
further including a coupling agent for aiding in adhering said
blend of inorganic antiblocking agents in said lower outer skin
layer.
29. The plurality of plastic sheets as specified in claim 28,
wherein said coupling agent is maleic anhydride-modified
polypropylene homopolymer.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This national application claims the benefit of the Apr. 29,
2015 filing date of PCT application PCT/US15/28281, which in turn
claims priority and the benefit under 35 U.S.C. .sctn.119(e) of
U.S. Patent Application Ser. No. 61/986,484, filed on Apr. 30,
2014, entitled, FILM FOR SHEET FED PRINTING, SHEETS FORMED FROM
SUCH FILM AND LABELS FORMED FROM SUCH SHEETS, the entire
disclosures of which is incorporated by reference herein.
BACKGROUND
[0002] 1. Field of the Invention
[0003] This invention relates generally to multilayer film
structures; to discrete sheets formed from said film structures for
use in a sheet fed printing operation, more specifically to sheets
to be fed into a high speed printer to form labels and other
printed sheet material. In addition, this invention relates to
employing the sheets in a sheet fed printing operation and also to
cut and stack labels and stack-fed in-mold labels formed from rolls
or sheets, said cut and stack labels being separable from a stack
and employed both as wrap around and spot labels on preformed
articles, e.g., containers, boxes, bottles, etc., and said
stack-fed in-mold labels being separable from a stack for in-mold
and cut and stack labeling applications.
[0004] 2. Background Art
[0005] A significant issue or problem in the high speed printing of
plastic sheets, preferably polyolefin sheets, is to achieve the
required separation of adjacent sheets to be printed to assure
proper feeding and printing of the individual sheets in a high
speed printing operation. It should be understood that individual
sheets directed to the printer have numerous applications,
including use in the formation of labels for various container
structures, including preformed structures and for use in in-mold
labeling.
[0006] In a high speed printing operation, individual sheets to be
printed can be fed from a stack or alternatively a continuous roll
of the multilayer film of this invention can be fed in-line through
a sheeting device located prior to the printer to form the
individual sheets that are then directed through the printer.
Whether the sheets are fed from a stack or continuously from a
roll, the individual sheets are positioned in a shingled
arrangement as they are being directed through the printer to
achieve the desired high speed printing operation. To further
explain, as a leading sheet is directed through the printer its
distal end is lifted to permit a proximal end of an adjacent
trailing sheet to be disposed under the distal end of the leading
sheet in a shingled arrangement. This provides the desired close
positioning between the proximal ends of the adjacent sheets to
achieve the desired high speed printing of the sheets, provided
that the shingled sheets properly separate from each other as they
are directed through the printing operation.
[0007] Thus, whether the sheets are in a stack prior to being
directed through the printer in a shingled arrangement or are
positioned in a shingled arrangement in a continuous printing
operation in which a roll of the multilayer film is sheeted prior
to the sheets being printed, a bottom surface of a leading sheet
needs to cleanly separate from an upper surface of an adjacent
trailing sheet so as not to adversely affect the printing
operation. In the case of sheets being fed from a stack the entire
bottom surface of a leading sheet engages an entire upper surface
of an adjacent trailing sheet prior to separation from the stack.
Thus, when sheets are to be fed from a stack an issue exists in
both cleanly separating adjacent sheets from the stack and then
subsequently separating adjacent sheets from their contacting,
shingled arrangement as they are being directed through the
printer. In the case of a continuous operation in which discrete
sheets are cut from a roll of film and then directed through the
printing operation in a shingled arrangement, only the distal end
of the bottom surface of the leading sheet engages the proximal end
of the upper surface of the adjacent trailing sheet and it is only
these engaging surface regions that need to be cleanly separated.
If adjacent contacting sheets are not cleanly separated from each
other a leading sheet can undesirably drag or move the trailing
sheet in contact with it as the leading sheet is being separated
from the trailing sheet and directed to, or through the printer.
This improper movement of the trailing sheet can be caused by
blocking between the engaging surfaces of adjacent sheets, the
build-up of static charges between the engaging surfaces and/or
frictional drag between those surfaces. The undesired blocking
effect is more common when the sheets have been maintained in a
stack for a significant period of time prior to printing. In this
case, the weight of the stack tends to expel air from between the
contacting surfaces of adjacent sheets to create the blocking
effect. However, the adverse effect of static charge build up
and/or frictional drag is prevalent in the high speed printing of
the sheets both from a stack of the sheets or in a continuous
printing operation in which the sheets are cut from a continuous
roll of multilayer film prior to be directed through the printing
operation.
[0008] In addition, regardless how labels are formed in a high
speed printing operation they often are provided in a stack; either
as cut and stack labels or as stack-fed in-mold labels. In either
case, contacting labels need to be cleanly separated from each
other. Thus the problems of providing reliable and correct
separation of sheets directed through a printer also apply to
stacks of labels formed from the sheets, or even from continuous
rolls in a roll-to-roll printing operation.
[0009] It is known that creating a roughened surface between
contacting, adjacent sheets or labels traps air between them to
prevent blocking, static charge build up and/or drag to aid in
permitting a leading sheet or label to move freely over and
separate from the underlying, engaging surface of an adjacent
trailing sheet or label to permit accurate separation and printing
of the individual sheets and accurate separation and application to
labels on products or into molds, in the case of in-mold labeling
processes.
[0010] One means of achieving a rough surface texture is to use
matte polymer compounds, generally composed of a physical mixture
of two immiscible polymers, i.e., homopolymer polypropylene and
high density polyethylene or other polyethylene structures.
However, it has been determined that the use of blends of
incompatible polymers can cause difficulties in processing the film
on a tenter line, especially when using a high crystalline
polypropylene (HCPP) in the core layer of the extruded film.
Specifically, the high processing temperature required to stretch
the HCPP in the machine direction can cause sticking of the matte
skin polymers on the machine direction orientation (MDO) rolls due
to the presence of the relatively low melting polyethylene in the
blend.
[0011] Although it has been suggested in the prior art to provide a
roughened surface by including anti-block materials in the surface
layer that protrude through the surface thereof, those suggestions
have been quite general; providing very little guidance in
selecting a desired combination of anti-block compounds for
providing the required roughened outer surface to permit the
continuous, reliable separation of individual leading and trailing
polyolefin sheets from each other as the individual sheets are
being directed to and/or through a high speed printing
operation.
[0012] Representative disclosures of using anti-block additives in
a skin surface or other layer of an oriented polyolefin film are
included in U.S. Pat. No. 6,623,866 (Migliorini et al.); U.S.
Publication No. 2003/0211298 (Migliorini et al.); U.S. Publication
No. 2012/0282447 (Gringoire et al.); European publication 026491
(Hayes); U.S. Publication 2007/0248810 (McGee et al.); U.S. Pat.
No. 6,939,602 (McGee et al.); International Publication WO
2011/162882 (Squire et al.) and International Publication WO
2009/042299 (Keung). The disclosures in these prior art
publications are fully incorporated by reference herein.
[0013] The Migliorini et al '298 publication discloses a multilayer
structure that can include anti-block agents in a lower or inner
skin layer thereof. The publication generally discloses that the
anti-block agents can include talc, and possible other additives
and provides a general disclosure that different sizes and shapes
can be blended together to optimize machinability. However, this
publication provides little guidance as to the manner in which
different anti-block agents should be combined to achieve any
desired result, and in fact is not directed to the issue of
enhancing separation of individual sheets in a stack to be fed into
a high speed printer.
[0014] The Migliorini et al. '866 patent also generally discloses
the use of a combination of organic and inorganic anti-block
additives, such as talc and PMMA, but discloses the use of those
additives in an inner or tie layer, not in an outer skin layer for
the purpose of enhancing separation of individual sheets in a stack
of sheets to be directed into a high speed printer.
[0015] In a similar vein, the Hayes '491 European publication also
discloses the use of organic and inorganic anti-block agents but
only in an internal substrate layer of a multilayer product.
Moreover, the general disclosure of employing organic and inorganic
anti-blocking agents does not include any details as to how those
materials should be combined to enhance separation of individual
sheets from a stack to be directed into a high speed printer.
[0016] The McGee et al. '810 publication also includes a general
disclosure of employing both an organic and inorganic anti-block
agent in a film to prevent blocking between a back-side adhesive
receiving coating and a front side layer intended to receive
printing thereon. This publication does not provide any guidance as
to the manner in which an organic or inorganic anti-block agent
should be combined to achieve the benefits that are desired and
achieved in the present invention, as will be discussed in greater
detail hereinafter.
[0017] The Squire et al. '882 international publication discloses
that polymethylmethacrylate is a well-known additive for use as an
anti-blocking agent and also states that inorganic particulates can
be used as an anti-blocking agent.
[0018] This publication states that the anti-block agent can be
incorporated into any of the layers, including the skin layer, but
does not provide any guidance as to a desired combination of
organic and inorganic additives that should be added for the
purpose of permitting separation of individual sheets in a stack to
permit such sheets to be directed through a high speed printing
operation.
[0019] ExxonMobil Oil Corporation U.S. Pat. No. 6,326,068 discloses
a multilayer film that can employ a blend of a non-distortable
organic polymer and an inorganic particle. Although the '068 patent
discloses employing blends of organic and inorganic anti-block
materials in a multilayer polyolefin film, this patent does not
disclose the combination of the specific antiblock components
within the specific amounts determined to be beneficially employed
in the present invention.
[0020] The McGee et al. '602 patent discloses a multilayer label
structure that employs an inorganic coating on the first side of a
first skin layer to prevent blocking. Exemplary coatings that are
generically identified are talc, colloidal silica and amorphous
silica.
[0021] The Gringoire et al. '447 publication discloses two side
coated composite films or labels and discusses the problem of prior
art films/labels blocking when the film is rolled or stacked. This
publication generically discloses a number of inorganic
compositions that can be employed as antiblock agents and includes
silica and talc in the listed compositions. The '447 publication
states that typically the inorganic material is present in an
amount from about 10 wt. % to about 70 wt. %; more preferably 35-50
and most preferably 10-30, wherein the inorganic material is a
silica. There is no specific disclosure of combining silica with
any other specific polymers and the percentages in which they
should be combined.
[0022] The Keung '299 International Publication discloses a
multi-layered opaque film including two skin layers. Exemplary
antiblocking agents that are disclosed include silica-based
products, PMMA and polysiloxanes. In addition, talc is disclosed as
being suitable filler. There is no disclosure of employing a
combination of any antiblock agents in any specified or desired
proportions.
[0023] It also has been disclosed in the prior art, particularly in
the formation of rigid plastic articles, to employ a coupling
agent, e.g., maleic anhydride-modified polypropylene homopolymer
and other polymeric and non-polymeric compositions, to aid in
adhering an inorganic material, such as talc, in a layer of the
product. The disclosed purpose of using the disclosed coupling
agents is to minimize the plating out of the talc during a
converting process. What is not disclosed or suggested in the prior
art is that the use of a maleic anhydride-modified polypropylene
homopolymer in individual multilayer films or sheets permits the
use of substantially lower quantities of talc than otherwise was
thought possible to achieve the desired separation from each other
of contacting surfaces of individual leading and trailing sheets as
they are fed through a high speed printing operation.
[0024] Prior to this invention, it was believed that a
substantially high level of finely divided talc particles on the
order of 25% by weight of the skin layer was required to permit the
desired feeding of individual sheets from the stack and/or shingled
arrangement into and through a high speed printer. In fact, it was
determined that employing such a large percentage of talc did
permit the required individual separation of sheets but created an
undesirable, excessive dusting problem that interfered with the
processing operation. The present invention achieves the desired
antiblocking, static reduction and reduction of drag between
adjacent leading and trailing sheets directed through a high speed
printing operation while also eliminating any undesired dusting
problem.
SUMMARY OF THE INVENTION
[0025] In accordance with this invention, individual plastic sheets
formed from a continuous roll of plastic film in accordance with
this invention are to be fed into and through a high speed printer
for forming printed labels and similar articles. The bottom surface
of the individual sheets engage an upper printable surface of
adjacent, trailing sheet when the sheets are fed from a stack
and/or when the sheets are in a shingled arrangement as they are
being fed through the printing operation. Each of the sheets
includes a core layer and opposing upper and lower outer skin
layers. The upper outer skin layer includes a polyolefin polymer as
the predominant component by weight thereof and this outer skin
layer is capable of receiving printed indicia thereon that is
applied by the high speed printer. The core layer includes a
polyolefin polymer as the predominant component, by weight,
thereof, and the lower outer skin layer includes a polyolefin
polymer as the predominant component by weight thereof.
[0026] In the formation of printed labels multiple labels are
printed on each sheet, or alternative from a roll, and the
individual labels cut from the sheet and stacked, usually in a
magazine, either as cut and stack labels or as stack-fed in-mold
labels.
[0027] The individual labels are then separated and individually
fed into labeling equipment to apply individual labels to the outer
surface of preformed articles, such as containers, or into a mold
for use in forming in-mold labels. Thus, this invention also
relates to cut and stack labels and to stack-fed in mold labels
regardless how the labels are formed, e.g., in a continuous
roll-to-roll printing operation or from the printing of individual
sheets.
[0028] The improvement in accordance with this invention resides in
the composition of the lower outer skin layer of the multilayer
roll of film; of the individual sheets formed from said roll and of
the stacked printed labels cut from the sheet or roll. It should be
noted that the individual labels cut from the printed sheets of
this invention are of the same multilayer structure as the sheets
of this invention and of the multilayer roll of film from which the
sheets are formed. In the cut and stacked arrangement the labels
have the same orientation of individual layers as the orientation
of the individual layers in the sheets and/or rolls, as directed
through a printing operation.
[0029] Thus, the structure of the lower outer skin layer of the
sheets of this invention, which permits the sheets to be
individually separated from upper printable surfaces of adjacent,
trailing sheets for feeding into a high speed printer, is the same
structure that exists in the lower outer skin layer of individual
labels cut from the sheets. This permits the labels to be
individually and cleanly separated from a stack of such labels to
carry out a desired labeling operation.
[0030] Although this invention primarily will be described in
connection with the structure of the individual sheets that are to
be fed through a high speed printer, the description applies
equally to the structure of the multilayer roll of plastic film
from which the sheets are formed and also to the printed labels cut
and stacked from the sheets for being fed individually into a
desired labeling operation, e.g., for labeling a preformed article
or for use in an in-mold labeling operation.
[0031] Specifically, the lower outer skin layer of the plastic
film, the sheets formed therefrom and the individual labels formed
from the sheets, includes a either a blend of organic and inorganic
antiblocking agents or a blend of only inorganic antiblocking
agents; said blend including less than 10% by weight of the lower
outer skin layer.
[0032] In one embodiment of this invention, the blend includes
polymethylmethacrylate (PMMA) (i.e., an organic antiblocking
compound) and talc (i.e., an inorganic antiblocking compound), the
talc being present in a higher percentage by weight than the
PMMA.
[0033] In the most preferred embodiment of the invention the blend
includes an organic antiblocking compound and at least two
inorganic antiblocking compounds; one of said inorganic compounds
is of an irregular particulate shape that is roughly spherical with
an irregular surface and the other of said inorganic compounds is
generally plate-like. In the most preferred embodiment the roughly
spherical particles are silica and the plate like particles are
talc. The preferred organic antiblocking compound is PMMA. In this
most preferred embodiment it has been determined that individual
sheets can be fed from a stack and through a printer at faster
speeds without dusting and with less double picking of printed
sheets from the stacks, than the prior art sheets and even faster
than sheets within the scope of this invention that include talc in
combination with either PMMA or silica.
[0034] In the preferred form of this invention, the lower outer
skin layer of each of the sheets includes less than 2% talc, by
weight, based on the weight of the lower outer skin layer and also
employs a coupling agent, e.g., maleic anhydride-modified
polypropylene homopolymer and possibly other polymer and
non-polymeric compositions for aiding in adhering the talc within
the lower outer skin layer, and further wherein the PMMA is present
in a weight percent of less than 1 based on the weight of the lower
outer skin layer.
[0035] In the most preferred embodiment of this invention, the
coupling agent is a maleic anhydride-modified polypropylene
homopolymer prepared by utilizing about 0.5% maleic anhydride and
the lower outer skin layer of each of the sheets includes between
1% and 2% talc, by weight, based on the weight of the lower outer
skin layer. The maleic anhydride-modified polypropylene homopolymer
is employed for aiding in adhering the talc in the lower outer skin
layer; with the PMMA being present in a weight percentage less than
0.5% based on the weight of the lower outer skin layer.
[0036] However, as discussed in greater detail herein, other
coupling agents are believed to be usable in this invention to bind
the talc into the structure to prevent undesired dusting. In
addition to being required to effectively bind the talc into the
structure, factors such as availability, cost, easy of processing,
etc. should be taken into account in selecting the coupling agent
for use in this invention.
[0037] Most preferably, when maleic anhydride-modified
polypropylene homopolymer is utilized as the coupling agent it is
present in a weight percent of about 5% based on the weight of the
lower outer skin layer and includes about 0.5% maleic anhydride
therein.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0038] This invention relates to a continuous, multilayer plastic
film and to individual plastic sheets cut from the film to be fed
through a high speed printer for forming printed labels and similar
articles. This invention also relates to printed labels formed from
the plastic sheets or directly from a roll of the plastic film.
[0039] Most preferably the continuous multilayer film from which
individual sheets or labels of this invention are cut is formed by
extrusion on a conventional tenter machine, and most preferably the
film is biaxially oriented in the formation process. The specific
equipment used to form single and multilayer plastic films is well
known in the art and does not constitute a limitation on the
broadest aspects of this invention. In addition, high speed
printers are well known in the art; the particular printer employed
to print the individual sheets not constituting a limitation on the
present invention.
[0040] However, it should be noted that the high speed printers
commonly employed in the formation of printed sheets include a
shingling device to lift the distal end of a leading sheet being
directed through the printer so as to receive the proximal end of
an adjacent trailing sheet under the distal end of the leading
sheet in a shingled arrangement. The shingled arrangement of the
adjacent leading and trailing sheets as they are being directed
through a high speed printer has been discussed in detail earlier
in this application. It should be noted that the shingled
arrangement is provided between adjacent leading and trailing
sheets directed through the printer, whether the sheets are
preformed and fed from a stack, or are continuously formed from a
roll of film prior to directing the sheets through the printing
operation.
[0041] As noted above, although this invention will be described
primarily with respect to the structure of individual plastic
sheets that are fed individually through a high speed printer, the
description that follows applies equally to the roll of plastic
films from which the sheets are formed and also to the individual,
printed labels cut and stacked from the sheets to be fed
individually from the stack to be applied to a desired article,
e.g., a preformed article or to an in-mold labeling operation where
the label is applied to an article as it is molded.
[0042] In other words, the specific structure and composition of
the layers in the individual sheets is the same structure and
composition as the plastic film from which the sheets are formed
and of the labels cut from the sheets. Moreover, the mechanism
permitting separation of adjacent, leading and trailing sheets as
they are directed to and/or through a high speed printing operation
is essentially the same mechanism permitting separation of
individual labels from a stack of such labels.
[0043] However, as noted earlier, when the sheets are separated
from a stack that has been maintained in a stacked condition for a
significant period of time prior to being directed to a printer,
air between adjacent, contacting sheet surfaces in the stack tends
to be expelled to enhance the undesired blocking of the adjacent
sheets being separated from the stack to be directed into and
through a high speed printing operation. Although the blocking
issue is not as significant when the sheets are continuously cut
from a roll of film and are directed through the printer in a
shingled arrangement, the undesired creation of static charges and
drag still exists, which can prevent the required "clean"
separation of the leading sheet from the underlying trailing sheet
as the shingled sheets are being directed through the printing
operation. This undesired failure of adjacent sheets separating
from each other results in skewed sheets at the in feed of a
printing machine or in two labels being simultaneously directed
through the in mold label picking operation at the same time, or
two cut and stack labels simultaneously being fed onto a container;
a problem generally referred to as "double picking." In less
typical printing from pre-cut sheets of film, as opposed to rolls
that are in-line sheeted, this problem is generally referred to as
a "double feed."
[0044] As will be pointed out in detail hereinafter, in the most
preferred embodiment of this invention, all of the polymers
employed in the film other than PMMA are polyolefins. The major
polymer component, by weight, in the core layer is a polypropylene
homopolymer; most preferably a high crystalline polypropylene.
[0045] Reference throughout this application to the film being a
"polypropylene" film refers to a film wherein the primary
component, by weight, in the core is a polypropylene homopolymer, a
high crystalline polypropylene homopolymer or a minirandom
copolymer.
[0046] A minirandom propylene copolymer includes ethylene in a
sufficiently small percentage to avoid adversely affecting the
crystalline properties of the polypropylene. Most commonly, the
percentage of ethylene by weight in the copolymer is less than 2%
and most preferably is 1% or less.
[0047] Reference throughout this application to "high crystalline
polypropylene" refers to a polypropylene having an isotactic index
of at least 95% and more preferably at least 98%.
[0048] Referenced throughout this application to "upper" and
"lower" in identifying the outer skin layers of multilayer sheets,
or labels formed from the sheet refer to the orientation or
position of the outer skin layers with the sheets and labels as
they are individually fed, respectively, into and through a high
speed printer and into a labeling operation.
[0049] It should be understood that the particular composition of
the core layer does not constitute a limitation on the broadest
aspects of this invention. However, this invention is particularly
beneficial for use in a multilayer film in which a high crystalline
polypropylene is the predominant polymer component of the core
layer, by weight. This provides the most desired stiffness to
labels formed from the sheets. Moreover, in forming opaque films a
voiding agent, e.g., calcium carbonate can be included in the core
in conventional, well-known amounts. This invention applies to both
clear and opaque films.
[0050] A unique feature of this invention for solving separation
and dusting problems, as discussed above, resides in the
composition of the lower outer skin layer. The skin layer includes
a unique and unobvious blend of antiblocking components in the
lower outer skin layer of the multilayer structures of the roll of
films, the sheets cut from the film and the labels or other printed
substrates formed from the sheets, as will be described in detail
hereinafter.
[0051] In accordance with this invention, a multi-layer polyolefin
film includes a central core layer and opposed upper and lower
outer skin layers. The number of layers can be varied in accordance
with the broadest aspects of this invention. However, the
multilayer film should be at least three layers; including a
central core and opposed upper and lower outer skin layers. If
desired, one or more intermediate tie layers can be employed in the
structure.
[0052] In a representative embodiment of this invention, the core
layer has a nominal thickness of 330 ga. (82.5 microns). In another
representative embodiment the core layer has a nominal thickness of
280 ga. (70 microns). The specific thickness of the core layer does
not constitute a limitation on the broadest aspects of the
invention. However, the core layer most preferably is the thickest
layer in the structure; far exceeding the thickness of outer skin
layers in a three layer structure. In a representative embodiment
of this invention, the core layer includes over 50% and more
preferably approximately 70% of a high crystalline polypropylene,
sold under the designation Braskem Inspire 6025 by Braskem America
having its corporate offices in Philadelphia Pennsylvania;
approximately 7.5% of a propylene/ethylene copolymer including 2.5%
by weight ethylene sold under the designation Braskem DS6D21 by
Braskem America; CaCO3 (voiding agent) and TiO2 (whitening agent)
in percentages conventionally employed to provide a white, voided
structure, and a small percentage of one or more slip agents, such
as Erucamide and Behenamide, as is well known in the art.
[0053] The specific formulation of the core layer described above
is for illustrative purposes and does not constitute a limitation
on the broadest aspects of this invention. For example, in clear
films the voiding agent will be omitted from the core.
[0054] However, as noted earlier herein, in the most preferred
embodiment of this invention a high crystalline polypropylene
constitutes the predominant polymer component by weight in the core
layer. The inclusion of a high crystalline polypropylene as the
predominant polymer component of the core layer yields a much
higher stiffness film than can be achieved using a typical film
grade homopolymer polypropylene. Such stiffness is highly desirable
in various label structures.
[0055] In a representative embodiment of this invention, both the
upper and lower outer skin layers have a thickness of approximately
10 ga. (2.5 microns) and the outer surfaces of both layers
preferably are oxidatively treated, e.g., by corona treatment. The
oxidative treatment of the upper outer skin layer enhances its
surface condition for receiving printed indicia thereon as is well
known in the art.
[0056] The oxidative treatment of the outer surface of the lower
outer skin layer actually enhances the ability of the final product
such as a label to be adhesively bonded to a substrate using any of
the commonly used adhesives for that purpose, such as a hot melt
adhesive.
[0057] The upper outer skin layer can be of any well know
composition suitable for receiving desire printed indicia thereon;
the specific composition not constituting a limitation on the
broadest aspects of this invention. For example, the outer layer
can include approximately 90% of a C2C3 copolymer and less than 5%
of a C2 homopolymer. In addition the upper layer can include other
well-known additives, such as slip agents and antistatic
agents.
[0058] As noted above, the specific composition of the upper outer
skin layer does not constitute a limitation on the broadest aspects
of this invention. However, it clearly is preferred to employ a
polyolefin as the predominant polymer component in the upper outer
skin layer and most preferably to employ a C2C3 copolymer, which
when oxidatively treated, is highly receptive to retaining printed
indicia thereon. However, other polymers and copolymers can be
employed, either alone or in combination with each other, e.g.,
C2C3C4 terpolymer, which are receptive to printed indicia.
[0059] The composition of the lower outer skin layer provides the
unique benefits achieved in this invention.
[0060] In accordance with the most preferred embodiment of this
invention the lower outer skin layer is predominantly a polyolefin
and includes a unique combination of organic and inorganic
antiblocking agents. Most preferably, at least two inorganic
antiblocking agents are employed; one being irregularly shaped and
generally spherical and the other being of a plate-like structure.
Most preferably the irregularly shaped, generally spherical
inorganic antiblocking agent is silica; most preferably a surface
treated synthetic amorphous silica. Most preferably the plate-like
structure is talc. Most preferably the talc has a d50=2-3
microns.
[0061] In the most preferred embodiment the organic antiblocking
agent is PMMA. In the preferred structure a coupling agent is
provided to bind together the particulate, antiblocking agents; one
well-known coupling agent being a maleic anhydride-modified
polypropylene homopolymer. In addition the lower outer surface,
like the upper outer surface, can include other well-known
additives such as slip and antistatic additives.
[0062] In the most preferred embodiment, the lower outer skin
layer, which is predominantly a polyolefin, includes an organic and
two inorganic antiblocking agents. This skin layer includes the
following antiblocking agents, by weight: 2500 ppm (0.25%) silica
(inorganic roughly spherical particulate material); 1.75% talc
(inorganic plate-like material) and 2500 ppm (0.25%) PMMA (organic
material). In addition, the lower outer skin layer includes a
coupling agent of 5%, by weight, preferably maleic anhydride
grafted polypropylene including 0.5% maleic anhydride, and also
conventional slip and antistatic agents well known in the art.
[0063] As noted above, in the most preferred embodiment of this
invention one of the inorganic antiblocking agents is a particulate
that is roughly spherical with an irregular shape (e.g., silica)
and the other inorganic antiblocking agent is generally plate-like
(e.g., talc). Although not wishing to be bound by any theory the
inventor believes that employing a combination of a roughly
spherical antiblock agent and a generally plate like antiblock
agents provides beneficial results because the combination of the
two differently shaped antiblocking agents generates additional
surface roughness, which allows for air entrainment between layers
of film, facilitating the sheet-fed layers of film to more easily
slide over one another in the printing process, and also for easier
dispensing of individual labels from a magazine in the labeling
operation.
[0064] In a second embodiment of this invention, the lower outer
skin layer is approximately 82%, by weight of the layer, of a C2C3
copolymer and also including both an organic and an inorganic
antiblock composition. The organic antiblock agent is PMMA and the
inorganic antiblock agent is talc, both being included in the same
weight percentages of the lower outer skin layer as set forth above
in connection with the most preferred embodiment (i.e., 2500 ppm of
PMMA and 1.75% talc). In addition, this lower outer skin layer
includes 5% of a maleic anhydride-modified polypropylene
homopolymer as a coupling agent for the particulate antiblocking
agents and also conventional amounts of slip and antistatic agents;
preferably the same slip and antistatic agents employed in the
lower outer surface of the most preferred embodiment of the
invention, as described above.
[0065] This latter-described, second embodiment has been determined
to provide benefits in both reducing double picking and increasing
printing speeds as compared to prior art sheets. However, the most
preferred embodiment described earlier performs even better than
this latter-described, second embodiment.
[0066] In a third embodiment of this invention, the lower outer
skin layer includes approximately 90% by weight of the layer of a
C2C3 copolymer including a small percentage, e.g. less than 5% of a
C2 homopolymer. In addition, this embodiment includes two inorganic
antiblock agents; one being a roughly spherical irregularly shaped
particle have an irregular surface (e.g., preferably silica) and
the other being a plate-like particulate material (e.g., preferably
talc). The percentage of silica, by weight of the lower outer skin
layer and the percentage, of talc, by weight of the lower outer
skin layer are approximately the same is included in the most
preferred embodiment of this invention (i.e., 2500 ppm silica and
1.75% talc). In addition, this third embodiment includes a coupling
agent for bonding the antiblocking agents together. Most preferably
the coupling agent is maleic anhydride grafted polypropylene
present at approximately 5% by weight of the lower outer skin
layer. As in the other embodiments of this invention other
additives in conventional amounts can be employed, such as slip and
antistatic agents.
[0067] This latter-described, third embodiment has been determined
to provide benefits in both reducing double picking and increasing
printing speeds as compared to prior art sheets. However, the most
preferred embodiment described earlier performs even better than
this latter-described, third embodiment.
[0068] It should be noted that in all embodiments the percentage of
antiblocking agents, by weight, in the lower outer skin layer is
less than 10%. Also, in all of the preferred embodiments the talc
had d50=2-3 microns.
[0069] It was not possible to predict the difference in performance
of the above described sheets of this invention by simply comparing
surface roughness values or coefficient of friction values of these
respective sheets. Taking into account standard deviations the
values for the respective three embodiments of this invention
overlapped; making it virtually impossible to predict that the most
preferred embodiment of this invention (multilayer polyolefin
sheets including one organic antiblocking agent and two inorganic
antiblocking agents in the lower outer surface), would perform
better than the second and third embodiments of this invention, as
described in detail above.
[0070] Also, the inclusion of a coupling agent presently is
considered to be an important component in the lower outer skin
layer to cooperate with the talc to secure or bind the talc into
the lower outer skin layer. Although the coupling agent presently
considered to be most preferred for use in this invention is a
maleic anhydride-modified polypropylene homopolymer, other coupling
agents are believed to be useable in this invention. In fact, in
accordance with the broadest aspects of this invention it may not
be necessary to use a coupling agent to bind the talc into the
lower outer skin layer.
[0071] As noted above, although maleic anhydride-modified
polypropylene homopolymer presently is considered the preferred
coupling agent usable in this invention, other coupling agents also
may be usable. For example, and not by way of limitation, silanes
(azido functional or amido styryl functional), organofunctional
silicone compounds, chlorinated hydrocarbons with and without
silane, Titanates, in situ polymerization of monomers, modified
polyolefins or an ethylene polar terpolymer such as Arkema's
LOTADER resins may be usable as coupling agents in this invention.
The above list of possible coupling agents is not intended to be
exhaustive; only to represent that a variety of types of coupling
agents may be usable in this invention. However, at the present
time maleic anhydride-modified polypropylene homopolymer is the
most preferred coupling agent usable in this invention. Therefore,
the description, which follows will be limited to the use of maleic
anhydride-modified polypropylene as the coupling agent employed in
the lower outer skin layer of the laminate structures of this
invention.
[0072] As presently understood by applicant, binding the talc into
the structure with a coupling agent such as maleic
anhydride-modified polypropylene homopolymer permits a substantial
reduction in the weight percent of talc that can be used to
cooperate with the PMMA in the lower outer skin layer to achieve
the required antiblock properties in accordance with this
invention. Specifically, as noted above, in accordance with the
most preferred embodiments of this invention the weight percent of
talc in the lower outer skin layer is less than 5%, while
cooperating with even a lesser percentage by weight of PMMA and/or
silica to provide the required antiblock properties for permitting
the desired separation of individual polyolefin sheets from a stack
and from a shingled arrangement during the feeding of the sheets
into a high speed printer at speeds that are faster than with the
use of prior art sheets. This use of a low percentage of talc in
conjunction with the coupling agent also reduces the amount of
dusting as compared to prior art structures.
[0073] It should be understood that although this invention has
been described in connection with a three layer sheet structure or
laminate, the number of layers in this structure or laminate can be
varied in accordance with the broadest aspects of this invention.
For example, the sheet or laminate can be formed with three, four,
five or even more layers if desired.
[0074] Moreover, the individual layers of the sheet can be
co-extruded or some of the layers can be applied by a separate
coating or extruding operation, either after the film has been
extruded and biaxially oriented, or after the film has been
oriented in the machine direction, but prior to the sheet having
been oriented in a transverse direction.
[0075] Numerous benefits are achieved in accordance with this
invention. Specifically, this invention provides, among other
benefits: (1) better label picking (de-stacking) of labels from a
magazine; (2) better finishing/processing of printed label sheets
before labels are cut therefrom; (3) decreased tendency for ink
offsetting (transfer from the upper print surface to the lower back
or outer surface of printed sheets in a stack before cutting labels
from the sheets and bundling them in a stack; (4) decreased
blocking tendency of labels in a stack; (5) reduced dusting and (6)
increased speeds in directing sheets through a printer without
double picking.
[0076] Although the present invention has been described in
connection with preferred embodiments thereof, it will be
appreciated by those skilled in the art that additions,
modifications, substitutions and deletions not specifically
described may be made without departing from the spirited scope of
the invention defined in the appended claims.
* * * * *